Threshing and chopping crop residue in an agricultural combine can create substantial amounts of small and lightweight crop residue particles, dust and fragments which are desirably discharged from the combine with the larger chopped crop residue. Apparatus having a straight blade portion for performing the chopping, that is, a substantially planar blade portion oriented in a direction of rotation of the rotatable element on which the apparatus is mounted, has been found to provide excellent chopping capability. Reference in this regard, Gronberg et al. U.S. Pat. No. 3,874,604, and Bender U.S. Pat. No. 4,998,679. However, this orientation provides only minimal air flow generation.
Other apparatus are configured to provide greater air flow generation. Reference in this regard, Redekop et al. U.S. Pat. Nos. 5,232,405; 5,482,508; and 6,478,674; and Hammarstrand U.S. Pat. No. 5,042,973. Of these, the blade member shown in U.S. Pat. No. 5,232,405 includes a support plate supporting a symmetrical transverse blade surface for generating a high velocity of air rotating with the chopping assembly. However, the symmetrical nature of the transverse blade about the support plate can be disadvantageous as it prevents the cutting edge of the blade member from being positioned close to fixed knives of the chopper past which the blade members move to perform the chopping action. The transverse blade is also only disclosed as lying in a plane perpendicular to the support plate and parallel to the rotational axis. And, as a result of the orientation of the blade relative to the support plate, the blade member is not reversible.
The apparatus of U.S. Pat. No. 5,482,508 overcomes the disadvantage of not being able to be positioned close to the fixed knives by having a fan blade extending sidewardly in only one direction from a trailing edge of the blade member. However, as a result of the sideward extent of the fan blade, this blade member is also not reversible and thus different blade members must be provided for use on opposite sides of a fixed knife of a chopper to achieve closeness of the cutting edge of the blade to the knife.
U.S. Pat. No. 6,478,674 is different still as it utilizes a twisted blade design. A disadvantage of this is that the cutting edge is oriented at an angle to the direction of rotation of the blade, which has been found to decrease cutting efficiency.
U.S. Pat. No. 5,042,973 discloses a chopper blade which is bent into a V or arch shape transverse cross section over the entire width of the blade, including the cutting edge or edges thereof, for providing a blower action. An observed disadvantage of the extension of the V or arch shape across the entire extent of the blade member is that it orients the cutting edge at an angle to the direction of rotation, thereby reducing cutting efficiency. Also, this makes the cutting efficiency and blower action inversely related. That is, as the angle of the V or degree of curvature is increased to increase the blower action, the angle of attack of the cutting edge of the blade relative to the direction of rotation thereof will also be increased, thereby decreasing cutting efficiency.
Therefore, what is sought is apparatus for a crop residue chopper which overcomes many of the disadvantages and shortcomings set forth above.